Transverse Spin Structure of the Nucleon through Target Single Spin Asymmetry in Semi-Inclusive Deep-Inelastic $(e,e^\prime \pi^\pm)$ Reaction at Jefferson Lab

TL;DR

This paper discusses a planned precision experiment at Jefferson Lab to measure transverse spin asymmetries in semi-inclusive deep-inelastic scattering, aiming to elucidate the nucleon's transverse spin structure and quark orbital angular momentum.

Contribution

It introduces a new experimental approach using a solenoid spectrometer and polarized helium-3 target to measure neutron asymmetries with high precision, enabling flavor separation and tensor charge determination.

Findings

Expected 10% accuracy in d-quark tensor charge

Precise 4-D data on Collins, Sivers, and pretzelocity asymmetries

Enhanced understanding of quark orbital angular momentum contributions

Abstract

Jefferson Lab (JLab) 12 GeV energy upgrade provides a golden opportunity to perform precision studies of the transverse spin and transverse-momentum-dependent structure in the valence quark region for both the proton and the neutron. In this paper, we focus our discussion on a recently approved experiment on the neutron as an example of the precision studies planned at JLab. The new experiment will perform precision measurements of target Single Spin Asymmetries (SSA) from semi-inclusive electro-production of charged pions from a 40-cm long transversely polarized $^3$He target in Deep-Inelastic-Scattering kinematics using 11 and 8.8 GeV electron beams. This new coincidence experiment in Hall A will employ a newly proposed solenoid spectrometer (SoLID). The large acceptance spectrometer and the high polarized luminosity will provide precise 4-D ($x$, $z$, $P_T$ and $Q^2$) data on the Collins, Sivers, and pretzelocity asymmetries for the neutron through the azimuthal angular dependence. The full 2$\pi$ azimuthal angular coverage in the lab is essential in controlling the systematic uncertainties. The results from this experiment, when combined with the proton Collins asymmetry measurement and the Collins fragmentation function determined from the e$^+$e$^-$ collision data, will allow for a quark flavor separation in order to achieve a determination of the tensor charge of the d quark to a 10% accuracy. The extracted Sivers and pretzelocity asymmetries will provide important information to understand the correlations between the quark orbital angular momentum and the nucleon spin and between the quark spin and nucleon spin.